Devices for controlling the transverse movement of the warp threads of textile weaving machines, in particular of weaving machines having individual heddle movement, are basically known from numerous documents. In many of these publications, attempts are made to put forward suitable proposals so that the problematic weaving harness of a shedding device of a Jacquard machine can be dispensed with.
EP 0 353 005 A1 discloses a drive arrangement for controlling the transverse movement of the warp threads, in which, with a linear motor, a closed drive cord for the heddles which is guided via four rotating rollers is proposed. However, the implementation of the invention disclosed in EP 0 353 005 A1 comes up against difficulties which are based, on the one hand, on the fact that, with a relatively large number of warp threads arranged next to one another, sufficient space could not be made available for a large number of linear motors, but also for the deflecting rollers, and, on the other hand, on the fact that the deflection of the linear motors proposed there was, in a justifiable version, too small for the necessary transverse movements of the warp threads.
It is known from WO-A-98/24955 to tension-mount the driving part of a weaving machine—in this case, a heddle or a heddle shaft—between two spring parts and to provide an electric drive which raises or lowers the driving part, together with the warp threads, for shedding purposes. This invention also discloses the proposal to design the above-described arrangement as a free oscillator such that a large part of the kinetic energy from the elastic spring force is applied, while the electric drive is intended rather as compensation for the energy losses and to activate the corresponding device. However, the version with the two springs in WO-A-98/24955 likewise takes up a relatively large amount of space, as may also be gathered from the drawings there. Furthermore, it seems difficult, in the arrangement proposed in WO-A-98/24955, on the one hand, to keep the build of the electric motor small, but, on the other hand, to design it with such high power and high movement that it fulfills the requirements when a multiplicity of warp threads lying next to one another are to undergo shedding.
Further publications, such as, for example, WO-A-/11327 or WO-A-2006/114188, are likewise concerned with a free oscillator arrangement, but without being able to solve the problems mentioned above.
EP 1 063 326 A1 discloses cord drives for the heddles of a textile weaving machine having individual heddle movement, and it is proposed there to wind the cords on one side onto electromotively driven cord rollers and to keep them tensioned on the other side by means of a helical spring fastened to the loom. However, the principles of a free oscillator, which are already known from the document mentioned above, are not implemented by means of the device from EP 1 063 326 A1.
Finally, WO-A-2006/063584 discloses a shedding device with individual thread control, in which, in a basically known way, a lifting spring frame or a fixed spring frame with a retaining element for the individual heddles is proposed. However, this type of shedding has proved to be susceptible to faults, since the retaining elements mentioned are basically temperamental.
EP 0 347 626 A2 and DE 198 49 728 A1 disclose electromotive drives for the shedding of weaving machines, which have a coil and a sheet-like permanent magnet, by means of which a rotational movement is proposed for shedding. In this case, a lever action (step-up) is proposed in EP 0 347 626 A2.